Maybe somebody can help me, I'm getting frustrated here.

I have Suddenlink service (50 down, 5 up) in B/CS. About two months ago, my service seemed to drop a lot so I thought that either my old modem was at the end of its life, or maybe there was something going on in the wires since they just finished building some new houses right next to me.

I bought a replacement modem (DOCSIS 3.0) but service did not improve. I had Suddenlink send out a technician who couldn't find anything wrong outside or inside. So he said that it must be my (new) cable modem. Interestingly, right after he left, everything was working fine. No problems at all - for a little less than a month. Then the problems started again (speeds suddenly dropped). So I returned the modem to Amazon and got a new one, just in case that really was the problem.

Now with the (second) new cable modem, everything has been working just fine again until a few days ago (once again, a little less than a month). And the issues are the same. My speeds will suddenly plummet to 10Mbps or less, but then they'll go back up to 50 again after a few minutes.

I've called tech support but they say they don't see any issues on their end. So I'm not sure what to do. I have a hard time believing I've got another faulty cable modem (that had no problems at all until a month after I purchased it). But my speeds drop both on WiFi and my wired desktop.

Any suggestions? What could I be missing?
I have an ARRIS SB6183 DOCSIS 3.0 cable modem and a Netgear ORBI router (one master, one satellite). As far as I can tell, all firmware is up to date.

If you power cycle the modem does everything work ok for a little while?

Is there any noticeable pattern to the speed drop? Like does it slow down and then stay slowed down? Or does it happen at a particular time of the day?

No noticeable pattern. I'll be working away just fine and it'll drop for a few minutes, then be back to normal again just fine. I work during the day so I mostly notice at night but it did happen during the day today.

If I cycle the modem, things are fine but then it happens again. I feel as if everything was perfectly fine for a month or so and then it started.

Hmm... It's not overheating by chance is it? Sometimes when they overheat they can slow down or even drop the connection for a bit. It could also be router that's overheating slowing things down. Try connecting directly to the modem and seeing what happens the next time it slows down.

I think cable companies are pretty good about capping individual modems to prevent a bandwidth hog.

I'm not an expert on knowing what it all means, but you can try checking the modem's internal log. You typically access it by going to http://192.168.0.1 on the Motorolas and the default username is admin, password is either blank, "admin", or motorola. If it's not that address/password check in the manual, I've got a netgear modem so I'm not sure.

Yeah, hard to say what's really going on without seeing details from the cable modem itself. As suggested, log in and see if you can get to a screen showing upstream and downstream power levels, SNR, and correctable/uncorrectable symbols. The sweet spot for DOCSIS is between -10 and 10 dBmV for downstream power, SNR > ~35 dB, and upstream power no greater than about 45-48 dBmV. Ideally you won't see any symbol errors, but correctables are ok (they won't cause connection issues since the definition of a correctable is data corruption that managed to get recovered through forward error correction built into the protocol itself). Uncorrectable symbols are bad... this means that you're essentially getting data loss that will trigger a re-send from the other side, resulting in poor throughput if it gets bad enough. However, you'll likely need to see uncorrectables into the hundreds of thousands or millions (within a fairly short time period) for it to be a real issue. I'd recommend power cycling the modem before looking at the stats to ensure that you're working with a known time period for collection.

If you see bad SNR or lots of symbol errors, you likely have a weak signal or ingress into your cable line that's causing interference. Cellular (particularly LTE signals operating in the 700-800 MHz band) have been really bad news for cable systems lately. You'll want to check all of your connectors, splitters, etc. to make sure that you don't have an obvious point for signal intrusion. Also, open ports are bad (wall jacks connected to a splitter but not being used).

In addition to the above, check that the cable and cable ends look good. While watching the SNR and other counters, try wiggling the cable at the wall.

I've encountered an poorly installed RG6 cable end causing poor signal. Replacing the end fixed the issue.

On top of the above suggestions regarding checking the connection between the wall jack and modem, do you have any other devices plugged into coax anywhere else in your house? If so, try disconnecting everything else from their respective wall coax connections and see if that affects your speed.

Along a similar lines, check any coax splitters between your cable modem and the service line. I had a splitter start going bad that would intermittently cause crazy signal issues until I finally found it in the attic and replaced it.

Thanks all. I'll start checking connections to see if that does anything. I happen to be working from home this morning and things just dropped. Getting 9Mbps download right now.

I don't suspect overheating. The modem is a touch warm but no more than I would expect it to be.
I'll go ahead and monoprice a new coax cable, that certainly doesn't hurt. That will let me check connections directly from the wall to the modem. I don't have anything else in the house plugged into a coax.

The Suddenlink guy said all the splitters were fine when he was here two months ago, both in the wall as well as outside. I'll post statistics if I can figure out how to get them.

Just powered the modem off and back on again. Here is what I see, I hope somebody knows what this means. Because it's all numbers to me.

First link is immediately after powering off/on the modem.
http://imgur.com/a/vUOOm
Second link is after fiddling around a bit with the cable connection.
http://imgur.com/AVmeDWT


Ugh. Can't even post a stupid image correctly... Sorry.

Another data point for anybody who might have some more ideas. Internet is extremely bad right now (under 10 Mbps). Just logged in and the values are just about the same as after the reboot.

This is my desktop which is wired into my router.
Channel 11 has -3.8 dBmV, 40.7 dB, 752 corrected and 24 uncorrectables.


Tell me if I'm wrong, but that makes me think the issue isn't at the cable modem.

So, I wish I could help you figure out what all the means. If it was me I'd just be googling those numbers and seeing what other folks with problems have and seeing what they ended up doing.

But, a faster way might be to call Motorolla customer support and say that your ISP said there's something wrong with the modem and then give them all that data, and see what they have to say. If you get someone semi-competent on the phone, they should be able to help you figure out what it all means.

My guess would be you've got a cable/connection problem, not a modem problem.

Well it seems my issue has been solved by purchasing a new coaxial cable for a couple bucks off Amazon. I appreciate the advice everybody gave, hopefully this thread helps somebody else in the future. Wish Suddenlink had recommended this from the beginning instead of telling me to exchange my cable modem. Guess I should have gone to TexAgs first.

texasaggie04 said:

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Well it seems my issue has been solved by purchasing a new coaxial cable for a couple bucks off Amazon. I appreciate the advice everybody gave, hopefully this thread helps somebody else in the future. Wish Suddenlink had recommended this from the beginning instead of telling me to exchange my cable modem. Guess I should have gone to TexAgs first.

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TexAgs, we definitely know more stuff than the idiots manning the call center for Suddenlink.

Glad you got your problem solved, but just for reference, 24 uncomfortable is very low. When i was having issues from that, my uncorrectables would be 5 and 6 figures per channel within a day of rebooting the modem. My fix came from pointing my router to a different DNS server than the comcast one.